Differential analysis for high density tiling microarray data.

Background: High density oligonucleotide tiling arrays are an effective and powerful platform for conducting unbiased genome-wide studies. The ab initio probe selection method employed in tiling arrays is unbiased, and thus ensures consistent sampling across coding and non-coding regions of the genome. These arrays are being increasingly used to study the associated processes of transcription, transcription factor binding, chromatin structure and their association.

Intrinsic histone-DNA interactions and low nucleosome density are important for preferential accessibility of promoter regions in yeast.

In yeast cells, preferential accessibility of the HIS3-PET56 promoter region is determined by a general property of the DNA sequence, not by defined sequence elements. In vivo, this region is largely devoid of nucleosomes, and accessibility is directly related to reduced histone density. The HIS3-PET56 and DED1 promoter regions associate poorly with histones in vitro, indicating that intrinsic nucleosome stability is a major determinant of preferential accessibility.

Unbiased mapping of transcription factor binding sites along human chromosomes 21 and 22 points to widespread regulation of noncoding RNAs.

Using high-density oligonucleotide arrays representing essentially all nonrepetitive sequences on human chromosomes 21 and 22, we map the binding sites in vivo for three DNA binding transcription factors, Sp1, cMyc, and p53, in an unbiased manner. This mapping reveals an unexpectedly large number of transcription factor binding site (TFBS) regions, with a minimal estimate of 12,000 for Sp1, 25,000 for cMyc, and 1600 for p53 when extrapolated to the full genome. Only 22% of these TFBS regions are located at the 5' termini of protein-coding genes while 36% lie within or immediately 3' to well-characterized genes and are significantly correlated with noncoding RNAs.